Answer to Switching Knights challenge
The minimum number of moves is 12. There are 10 pieces to be moved, so the theoretical minimum of 10 moves could work only if each piece moves only once. But no first move exists that would place a piece immediately into its target position, so the first piece and the last piece need to move twice. When working this solution, remember to never, ever put a piece into any of the corners! Then the solution works almost automatically.
Both Robin King and Ea Ea sent in elegant and detailed mathematical proofs that 12 moves are the minimum. But we knew that.